Scaffolding

ABSTRACT

A post assembly has a free-standing upright, a wall mount assembly, a platform support assembly, a cylinder mounting bracket and a hydraulic cylinder. The wall mount assembly is engaged with the upright proximal the top end for mounting the upright to a building structure. The platform support assembly has a slide tube movably engaged with the upright, one or more platform support arms mounted to the slide tube for supporting one or more platforms, and a lock for engagement with the upright to prevent downward movement of the slide tube. The cylinder mounting bracket is movably engaged with the upright and has a lock for engagement with the upright to prevent downward movement of the cylinder mounting bracket. The hydraulic cylinder is mounted to the slide tube assembly and the cylinder mounting bracket. The hydraulic cylinder is actuable to produce relative vertical movement between the slide tube and the cylinder mounting bracket by moving either the slide tube or the cylinder mounting bracket. Two or more post assemblies may be used together to form a height adjustable scaffolding system.

FIELD OF THE INVENTION

The present invention relates to scaffolding, especially to height adjustable scaffolding and post assemblies therefor for lifting heavy materials, for example masonry or stone products.

BACKGROUND OF THE INVENTION

External walls of a building structure are often faced with a stone or masonry product (e.g. brick, block, stone tile, slate, etc.) for reasons of enhanced aesthetics and/or structural strength. Facing a wall with stone or masonry product requires people with specialized skills and a way of lifting the heavy product to higher elevations so that a workman can face upper levels of the wall.

Typically, scaffolding systems are erected to provide platforms at the necessary height to face the wall. However, lifting the product to the height of the platform is difficult and scaffolding systems currently available in the are generally capable of supporting only limited weight. Consequently, a workman wastes much time and energy climbing up and down the scaffolding system to both supply more product to the platform and raise and lower the platform to the desired height. This is not only a waste of valuable time, it is a safety hazard as well since most accidents on a site occur while setting up the scaffold system or transporting the product.

One solution to the problem has been to provide more workmen to do some of the jobs thereby freeing the person with the specialized skills to do more of the facing work. While somewhat effective, more workmen results in increased costs and does not solve the problem of having to constantly climb off the scaffold to raise and lower the platform.

To solve the latter problem, many height adjustable scaffolding systems have been developed employing a variety of mechanisms to raise and lower the platforms. However, such systems are typically plagued with one or more problems, for example, an inability to raise and lower the platform evenly on both ends, inability to support the great weight required for stone and masonry products, inability to easily expand the system to cover walls of greater length and/or height, inability to provide convenient access to stone or masonry product on the scaffolding system, and inability to conveniently adjust the height of the platforms over an incrementally smaller distance.

There remains a need in the art to provide a convenient and safe height adjustable scaffolding system, particularly for working with heavy material.

SUMMARY OF THE INVENTION

There is provided post assembly for a height adjustable scaffolding system for lifting heavy materials comprising: a free-standing upright comprising an elongated strut having a top end and a bottom end; a wall mount assembly engaged with the upright proximal the top end of the elongated strut for mounting the upright to a building structure; a platform support assembly for supporting two or more platforms between two or more post assemblies, the platform support assembly comprising a slide tube movably engaged with the upright to permit vertical movement of the slide tube between the top and bottom ends of the elongated strut, two or more platform support arms mounted to the slide tube for supporting two or more platforms, first locking means for engagement with the elongated strut for preventing downward movement of the platform support assembly; a cylinder mounting bracket movably engaged with the upright to permit vertical movement of the cylinder mounting bracket, the cylinder mounting bracket comprising second locking means for engagement with the elongated strut for preventing downward movement of the cylinder mounting bracket; and, a hydraulic cylinder having a first end and a second end, the first end mounted to the slide tube, the second end mounted to the cylinder mounting bracket, the hydraulic cylinder actuable to produce relative vertical movement between the slide tube and the cylinder mounting bracket by moving the slide tube or the cylinder mounting bracket.

There is also provided a height adjustable scaffolding system comprising: two or more post assemblies of the present invention, the upright of each post assembly spaced-apart from and mounted to the building structure; two or more platforms extending between adjacent post assemblies supported on the platform support arms of the adjacent post assemblies; a power source for powering the hydraulic cylinder of each post assembly; and, control means for providing simultaneous control of power to all of the hydraulic cylinders.

The elongated strut of the upright may be of any suitable length and diameter. Two or more elongated struts may be linked together by a connector to provide additional length to the post assembly and additional height to the scaffolding system. Preferably, the elongated strut comprises a square tube. Preferably, the elongated strut has a foot at the bottom end for resting on the ground or other relatively flat surface. The foot may comprise a flat plate to distribute load on the strut over a larger surface area. The upright may comprise a brace mount located near the top of the elongated strut to permit securing of the top of the post assembly to the ground by means of a brace attached to the brace mount and the ground. The brace may comprise guy wires, rods or like means.

The elongated strut is preferably housed within the slide tube. The elongated strut is also preferably housed within the cylinder mounting bracket. The slide tube and cylinder mounting bracket are movably engaged with the upright to permit vertical movement of the slide tube and cylinder mounting bracket on the upright. In one embodiment, the slide tube and/or cylinder support bracket are square tubes having diameters that permit the elongated strut to slide therein. The slide tube and/or cylinder mounting bracket may comprise means to reduce the possibility of binding to the elongated strut during vertical movement, for example, bearings or low friction inserts or coatings. In a preferred embodiment, one or more bearings may be used to reduce binding between the elongated strut and the slide tube and/or cylinder mounting bracket. Where the slide tube and cylinder mounting bracket are square tubes, it is advantageous to provide bearings on all four faces of the square tubes.

The slide tube and cylinder mounting bracket each have locking means that can engage the elongated strut to prevent downward movement of the slide tube and cylinder mounting bracket. The elongated strut may comprise means for cooperating with the locking means to ensure more secure locking. Locking means may comprise, for example, a pin or a sprocket or a combination of means that engages the elongated strut. The elongated strut may comprise apertures or protrusions that cooperate with the pin or sprocket for more secure engagement of the locking means.

In a preferred embodiment, the locking means comprises a pin for engagement with a plurality of vertically spaced apertures on the elongated strut. The pin may be biased, for example by a spring, for engagement with the apertures. The pin may comprise means for selective disengagement of the pin from an aperture.

Mounted to the slide tube are two or more, preferably two, platform support arms. When two or more post assemblies are used in spaced-apart configuration, the platform support arms support a platform between the two or more post assemblies. Preferably, there are two platform support arms mounted to the slide tube, a lower one for supporting a walker platform in front of the post assembly and an upper one for supporting a loader platform in back of the post assembly (i.e. on the side opposite the lower platform support arm) and above the loader platform.

One or more hydraulic cylinders are mounted between the slide tube and the cylinder support bracket for producing relative movement between the slide tube and the cylinder support bracket. It is this relative movement that permits height adjustment of the scaffold. So that the slide tube and cylinder support bracket may each be raised and lowered independently, it is preferable to use a double-acting hydraulic cylinder or a pair of single-acting hydraulic cylinders mounted in reverse orientation. Control and power of hydraulic cylinders may be accomplished by methods generally known in the art.

Preferably at least one of the platform support arms is positioned between the first and second ends of the hydraulic cylinder. Such an arrangement provides a more compact and efficient post assembly that has more useful working range for a given length of the elongated strut.

In a scaffolding system of the present invention, the upright is spaced-apart from the building structure to provide space between the structure and the upright for a platform. For masonry and stone work, this space is preferably about 27 to 30 inches top provide sufficient space to work while being as close to the building structure as possible. In operation, the upright is free standing. In order to prevent the upright from falling over, the wall mount assembly permits securing the upright to the building structure to provide stability to the post assembly. The wall mount assembly is preferably movably engaged with the upright to permit vertical movement of the upright when the wall mount assembly is fixedly mounted to the building structure. This permits the building and/or upright to move in response to ground movement or other causes without placing a strain on the mounting connection of the wall mount to the building structure. Preferably, the wall mount assembly comprises a square tube in a manner similar to the slide tube and cylinder support bracket. Preferably, the wall mount assembly also comprises means for reducing the possibility of binding on the elongated strut, for example one or more bearings or low friction inserts or coatings.

The scaffolding system of the present invention comprises two or more post assemblies. For ease of operation, it is preferable to provide a means for simultaneous selective disengagement of the first locking means on all post assemblies. It is also preferable to provide a means for simultaneous selective disengagement of the second locking means on all post assemblies. Such means may comprise a mechanism (e.g. a lever, cable, pulley, etc. or a combination thereof) connected to all of the first locking means or all of the second locking means. Connection of the lever to the locking means may be accomplished, for example, by cables, rods, bars, etc. or a combination thereof.

The scaffolding system may comprise a back-up support system, for example security bolts or a winch and cable system, as a redundant security measure and/or to be able to effect more rapid lowering of support platforms. The post assembly may be equipped with dumb waiters in the slide tube and cylinder mounting bracket to prevent crashing of the platforms if both are unlocked at the same time.

When used to lift stone or masonry products, the post assembly of the present invention must support considerable weight. Therefore, in such applications, the post assembly should be constructed of strong, durable material, for example a metal or metal composite, for example iron, steel, etc.

The post assembly of the present invention advantageously permits adjusting the height of a scaffold over the entire length of the uprights from foot to wall mount assembly. This provides for a greater range of heights and more increments of heights over a given length of uprights than prior art scaffolding systems.

Further, height adjustment of the scaffold can be accomplished without having to move planks of the platform. Therefore, height adjustment of the scaffold may be accomplished with loaded platforms. If desired, height adjustment may be advantageously accomplished by a single workman from the walker platform. The workman need not leave the walker platform to adjust the height of the scaffold. Masonry or stone product is conveniently located at hip height to the workman at all times. Such advantages provide great savings in time and effort and enhance safety at the job site.

Furthermore, the scaffolding system of the present invention can support heavier loads than prior art systems. Each post assembly of the present invention can support up to 3000 lbs., as opposed to 700 lbs. for most prior art systems. Additionally, the scaffolding system is close to the wall (within 3 feet) for greater convenience for the workman.

Further features of the invention will be described or will become apparent in the course of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more clearly understood, embodiments thereof will now be described in detail by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a post assembly of the present invention;

FIG. 2A depicts the slide tube of the post assembly of FIG. 1 as viewed from the side of the post assembly;

FIG. 2B depicts the slide tube of FIG. 2A as viewed from the front of the post assembly;

FIG. 2C depicts the slide tube of FIG. 2A as viewed from the top end of the post assembly;

FIG. 3A is a perspective view of the cylinder mounting bracket of the post assembly of FIG. 1;

FIG. 3B depicts the cylinder mounting bracket of FIG. 3A as viewed from the side of the post assembly;

FIG. 3C depicts the cylinder mounting bracket of FIG. 3A as viewed from the front of the post assembly;

FIG. 3D depicts the cylinder mounting bracket of FIG. 3A as viewed from the top end of the post assembly;

FIG. 4A is a perspective view of a locking pin on the post assembly of FIG. 1;

FIG. 4B depicts the locking pin of FIG. 4A as viewed from the side of the post assembly;

FIG. 4C depicts the locking pin of FIG. 4A as viewed from the front of the post assembly;

FIG. 4D depicts the locking pin of FIG. 4A as viewed from the top end of the post assembly;

FIG. 5A is a perspective view of the wall mount assembly of the post assembly of FIG. 1;

FIG. 5B depicts the wall mount assembly of FIG. 5A as viewed from the side of the post assembly;

FIG. 5C depicts the wall mount assembly of FIG. 5A as viewed from the front of the post assembly;

FIG. 5D depicts the wall mount assembly of FIG. 5A as viewed from the top end of the post assembly; and,

FIG. 6 depicts a scaffolding system of the present invention having three post assemblies arranged in a row.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 5, a post assembly of the present invention comprises an upright comprising a 12 foot long 3″ square steel tube 10 having a plurality of apertures 11 vertically spaced at regular intervals along the front face of the 3″ tube. The bottom end of 3″ tube 10 is attached to foot 12 for supporting the post assembly on the ground or other relatively flat surface. Foot 12 comprises a flat plate perpendicular to 3″ tube 10 for distributing weight over a larger surface area to provide better stability and to help prevent the post assembly from sinking into then ground. The top end of 3″ tube 10 is attached to brace mount 13 which is a 3.5″ square steel tube fitted over 3″ tube 10. Brace mount 13 comprises a pair of sideways extending flanges 14 to which a brace may be connected for stabilizing the post assembly when it is the end post of a scaffolding system as described in relation to FIG. 6 below.

A 4 foot long 4″ square steel slide tube 20 having 3″ tube 10 encircled therein is vertically movable along the length of the 3″ tube. Connected to slide tube 20 are upper platform support arm 21 and lower platform support arm 22. The upper and lower platform support arms are connected to the slide tube by arm support brackets 23 within which the platform support arms are slidably engaged and secured with a bolt or pin. Upper arm 21 extends perpendicularly from the rear face of slide tube 20 and lower arm 22 extends perpendicularly from the front face of the slide tube. Upper arm 21 is used to support a loader platform of a scaffolding system while lower arm 22 is used is used to support a walker platform. To help prevent slide tube 20 from binding on 3″ tube 10 during vertical movement of the slide tube, eight bearings 24 are mounted in upper and lower sets on each face of the slide tube. Bearings 24 extend through the wall of slide tube 20 to engage the faces of 3″ tube 10. Bearings 24 can rotate as slide tube 20 moves vertically, either up or down. Security bolts 78,79 on each side of the 4″ tube may be screwed in, if desired, to engage the sides of the 3″ tube as an added safety measure to prevent the 4″ tube from accidentally moving. If the security bolts are engaged, they will need to be disengaged by screwing them out before height adjustment of slide tube 20 can be effected.

At a desired height, slide tube 20 is locked into place on 3″ tube 10 by engagement of spring-loaded locking pin 25 in one of the apertures 11 in 3″ tube 10. Spring-loaded locking pin 25 is mounted on the front face of slide tube 20 and is biased toward the front face of 3″ tube 10. As best seen in FIG. 4B, tip 31 of pin 25 is sloped on its upper surface to permit automatic disengagement of the pin from the aperture in response to upward movement of slide tube 20. Pin 25 will automatically bias into place in the next aperture up as slide tube 20 moves upwardly. Tip 31 of pin 25 is horizontal on its bottom surface to ensure that slide tube 20 cannot move downwardly without actively disengaging the pin from the aperture.

When downward movement of the slide tube is desired, pin 25 may be disengaged from aperture 11 by pulling the pin out of the aperture. This may be conveniently accomplished by action of swivel link 26. Referring particularly to FIG. 4, swivel link 26 comprises a set of steel bars pivotally linked on pins 34. In particular, one leg of L-shaped bar 36 is pivotally linked to one end of pin pulling bar 37 and the corner of L-shaped bar 36 is pivotally linked to one end of fixed pin bar 38. The other end of pin pulling bar 37 is pivotally linked to tail end 32 of pin 25 and the other end of fixed pin bar 38 is fixedly attached to housing 33 of pin 25. The other leg of L-shaped bar 36 may be pivotally connected to hook 27 such that an appropriate force on the leg of L-shaped bar 36 connected to the hook causes pin 25 to be pulled out of the aperture by pin pulling bar 37. A workman standing on the walker platform may thus use hook 27 to pull pin 25 from aperture 11.

Once the pin is pulled from the aperture, slide tube 20 is movable downward on 3″ tube 10. Especially where a large number of post assemblies are used to construct a scaffolding system, hook 27 on each post assembly may be conveniently replaced by a rod or tube extending between and connected to swivel links 26 of all post assemblies and the rod or tube connected to a single lever mounted near the walker platform so that action on the lever will release pins 25 on all post assemblies simultaneously.

Proximal the top of slide tube 20 under arm 21 but above the upper set of bearings 24, bracket flanges 28 extend perpendicularly from the rear face. Bracket flanges 28 are connected to the top end of double-acting hydraulic cylinder 35 by means of draw pin 29. Draw pin 29 may be secured by a cotter pin (not shown).

A cylinder mounting bracket comprises 6″ long 4″ square steel cylinder mounting tube 40 separate from and located below slide tube 20. Cylinder mounting tube 40 is vertically movable along the length of 3″ tube 10 in a manner similar to that of slide tube 20. Thus, bearings 44 help prevent binding of cylinder mounting tube 40 and spring-loaded pin 45 locks the cylinder mounting tube at a desired height by engagement of the pin 45 in an aperture 11 in 3″ tube 10. The action of pin 45 is the same as that described for pin 25 above. Releasing pin 45 from aperture 11 is accomplished by action on swivel link 46 in the same manner as described above in connection with swivel link 26. In the same manner as described above, pins 45 on a plurality of post assemblies may be released individually or simultaneously.

Bracket flanges 48 extend perpendicularly from the rear face of cylinder mounting tube 40 and are connected to the bottom end of double-acting hydraulic cylinder 35 by means of draw pin 49. Draw pin 49 may be secured by a cotter pin (not shown). Hydraulic cylinder 35 has a lift height of 30 inches.

The bottom end of hydraulic cylinder 35 is connected to cylinder mounting tube 40 as close as possible to the ground. The top end of hydraulic cylinder 35 is connected to slide tube 20 as close as possible to the top of the slide tube while remaining below the upper platform support arm 21. As a result, upper platform support arm 21 and lower platform support arm 22 are as close to the ground as possible when slide tube 20 and cylinder mounting tube 40 are in the lowermost position on 3″ tube 10. This is particularly beneficial when working with heavy materials. In such an arrangement, lower platform support arm 22 is always positioned between the top and bottom ends of the hydraulic cylinder providing a more compact and efficient post assembly that has more useful working range for a given length of the 3″ tube.

A wall mount assembly is located below brace mount 13 proximal the top of 3″ tube 10 and extends perpendicularly from the front face of 3″ tube 10. The wall mount assembly comprises 8″ long 4″ square steel wall mount assembly tube 50 separate from and located above slide tube 20. Wall mount assembly tube 50 is vertically movable along the length of 3″ tube 10 in a manner similar to that of slide tube 20. Thus, bearings 54 help prevent binding of wall mount assembly tube 50 to 3″ tube 10. Wall mount assembly tube 50 is allowed to ride freely along 3″ tube 10 to accommodate settling and heaving of the post assembly due to ground surface and/or building movement effects. Extending perpendicularly from the from face of wall mount assembly tube 50 is connector post 51, which connects the wall mount assembly tube 50 to mounting plate 52. Mounting plate 52 may be secured to a wall of a building structure by any convenient means, e.g. screws, bolts, etc., to stabilize the post assembly.

Referring to FIG. 6, a height adjustable scaffolding system of the present invention comprises three post assemblies 5 a,5 b,5 c similar to the one described in relation to FIGS. 1-5 lined up in a row. For safety and stability, the post assemblies are secured to a wall of a building (not shown) by fastening wall mount assemblies 50 a,50 b,50 c to the building. Upper platform support arms 21 a,21 b,21 c support loader platform 61 on which bricks may be stacked. Lower platform support arms 22 a,22 b,22 c support walker platform 62 from which a workman may do work. Walker platform 62 is located below and closer to the wall than loader platform 61 so that the stack of bricks is conveniently at hip height to the workman and on the opposite side of the post assemblies, which is both more convenient and safer for the workman.

The scaffolding system is further stabilized by securing end post assemblies 5 a,5 c to the ground using braces 66,67. Braces 66,67 are steel rods connected to post assemblies 5 a,5 c at brace mounts 13 a,13 c by a pin passing through apertures in the rods and in the pair of sideways extending flanges of the brace mounts. Braces 66,67 comprise ground plates 68,69 respectively, which are secured to the ground, for example by spikes.

Upper connecting rod 71 extends between and is connected to swivel links 26 a,26 b,26 c on the slide tube of each post assembly. The upper connecting rod is connected to a single lever (not shown) at the worker platform so that the spring-loaded pins of each slide tube may be released simultaneously by a single workman when the workman desires to adjust the height of the slide tubes on the post assemblies.

Lower connecting rod 72 extends between and is connected to swivel links 46 a,46 b,46 c on the cylinder mounting brackets of each post assembly. The lower connecting rod is connected to a single lever (not shown) at the worker platform so that the spring-loaded pins of each cylinder mounting bracket may be released simultaneously by a single workman when the workman desires to adjust the height of the cylinder mounting brackets on the post assemblies.

Using an upper connecting rod permits a single workman to simultaneously adjust the height of all of the slide tubes on the post assemblies. Using a lower connecting rod permits a single workman to simultaneously adjust the height of all of the cylinder mounting tubes on the post assemblies. If both upper and lower connecting rods are used, a single workman can conveniently adjust the height of the walker and loader platforms without having to leave the walker platform.

Double-acting hydraulic cylinders 35 a,35 b,35 c are connected by hydraulic supply lines to a common controller and power source (not shown).

Referring generally to the Figures, the way in which the height of the scaffolding system is adjusted will now be described in relation to a single post assembly. It will be understood that each post assembly in the scaffolding system operates similarly and that the operation of all post assemblies may accomplished simultaneously as previously described.

Starting with slide tube 20 and cylinder mounting bracket 40 in their lowest possible positions on post assembly 10, and starting with double-acting hydraulic cylinder 35 fully retracted, spring-loaded pins 25 and 45 will each be engaged within apertures 11 in the post assembly. In order to raise the walker and loader platforms, it is necessary to raise slide tube 20. The hydraulic power source is switched on and hydraulic fluid flow to hydraulic cylinder 35 is set to drive the cylinder's rod up and spring-loaded pin 25 is released from its aperture thereby allowing hydraulic cylinder 35 to extend, pushing slide tube 20 upward. When pin 25 is aligned with the next highest aperture in post assembly 10, spring-loaded pin 25 will automatically engage the next highest aperture thereby arresting upward movement of the slide tube. If cylinder 35 extends far enough and if apertures 11 are sufficiently close together, it may be possible to allow pin 25, and therefore slide tube 20, to pass by the next highest aperture to an aperture yet higher by maintaining action on swivel link 26 to keep spring-loaded pin 25 from engaging the next highest aperture.

Once hydraulic cylinder 35 is fully extended, it is necessary to raise cylinder mounting bracket 40 before the walker and loader platforms can be raised further. To raise cylinder mounting bracket 40, hydraulic fluid flow to double-acting hydraulic cylinder is reversed. Reversing hydraulic fluid flow may be accomplished from a controller mounted on the walker platform so that the workman does not need to leave the scaffolding system. Spring-loaded pin 45 is released from its aperture permitting hydraulic cylinder 35 to retract since pin 25 on slide tube 20 remains engaged within its aperture. Fluid pressure in double-acting hydraulic cylinder drives the cylinder's rod down thereby pulling the cylinder's body up. Retraction of hydraulic cylinder 35 brings cylinder mounting bracket 40 up until pin 45 engages the next highest aperture. By maintaining action on swivel link 46 it is possible to keep pin 45 from engaging the next highest aperture thereby permitting the cylinder mounting bracket to be brought up as high as possible.

To again raise slide tube 20, hydraulic fluid flow to double-acting cylinder 35 is again reversed to drive the cylinder's rod up and the foregoing raising process repeated. The entire raising process may be repeated until slide tube 20 can be raised no higher on post assembly 10 due to the presence of wall mount assembly 50 and brace mount 13.

With slide tube 20 and cylinder mounting bracket 40 in their highest possible positions on post assembly 10, and with double-acting hydraulic cylinder 35 fully retracted, spring-loaded pins 25 and 45 will each be engaged within apertures 11 in the post assembly. In order to lower the walker and loader platforms, it is necessary to lower cylinder mounting bracket 40. Hydraulic fluid flow to hydraulic cylinder 35 is set to drive the cylinder's rod up and spring-loaded pin 45 is released from its aperture thereby allowing hydraulic cylinder 35 to extend, pushing cylinder mounting bracket 40 downward. When pin 45 is aligned with the next lowest aperture in post assembly 10, spring-loaded pin 45 will automatically engage the next lowest aperture thereby arresting downward movement of the cylinder mounting bracket. If cylinder 35 extends far enough and if apertures 11 are sufficiently close together, it may be possible to allow pin 45, and therefore cylinder mounting bracket 40, to pass by the next lowest aperture to an aperture yet lower by maintaining action on swivel link 46 to keep spring-loaded pin 45 from engaging the next lowest aperture.

Once cylinder mounting bracket 40 is lowered, it is necessary to lower slide tube 20 in order to lower the walker and loader platforms. To lower slide tube 20, hydraulic fluid flow to double-acting hydraulic cylinder is reversed and spring-loaded pin 25 is released from its aperture permitting hydraulic cylinder 35 to retract since pin 45 on cylinder mounting bracket 40 remains engaged within its aperture. Fluid pressure in double-acting hydraulic cylinder drives the cylinder's rod down thereby retracting hydraulic cylinder 35. Retraction of hydraulic cylinder 35 pulls slide tube 20 down until pin 25 engages the next lowest aperture. By maintaining action on swivel link 26 it is possible to keep pin 25 from engaging the next lowest aperture thereby permitting the slide tube to be pulled down as low as possible.

To again lower cylinder mounting bracket 40, hydraulic fluid flow to double-acting cylinder 35 is again reversed to drive the cylinder's rod up and the foregoing lowering process repeated. The entire lowering process may be repeated until cylinder mounting bracket 40 can be lowered no lower on post assembly 10 due to the presence of foot 12 or the lowest aperture.

It is not advisable to release both pins 25 and 45 at the same time as this will permit both the slide tube and the cylinder mounting bracket to lower simultaneously causing the platforms to crash to the ground rapidly. One skilled in the art will understand that two single-acting hydraulic cylinders may be used in place of one double-acting hydraulic cylinder.

Other advantages which are inherent to the structure are obvious to one skilled in the art. The embodiments are described herein illustratively and are not meant to limit the scope of the invention as claimed. Variations of the foregoing embodiments will be evident to a person of ordinary skill and are intended by the inventor to be encompassed by the following claims. 

1. A post assembly for a height adjustable scaffolding system for lifting heavy materials comprising: (a) a free-standing upright comprising an elongated strut having a top end and a bottom end; (b) a wall mount assembly engaged with the upright proximal the top end of the elongated strut for mounting the upright to a building structure; (c) a platform support assembly for supporting two or more platforms between two or more post assemblies, the platform support assembly comprising a slide tube movably engaged with the upright to permit vertical movement of the slide tube between the top and bottom ends of the elongated strut, two or more platform support arms mounted to the slide tube for supporting two or more platforms, first locking means for engagement with the elongated strut for preventing downward movement of the platform support assembly; (d) a cylinder mounting bracket movably engaged with the upright to permit vertical movement of the cylinder mounting bracket, the cylinder mounting bracket comprising second locking means for engagement with the elongated strut for preventing downward movement of the cylinder mounting bracket; and, (e) a hydraulic cylinder having a first end and a second end, the first end mounted to the slide tube, the second end mounted to the cylinder mounting bracket, the hydraulic cylinder actuable to produce relative vertical movement between the slide tube and the cylinder mounting bracket by moving the slide tube or the cylinder mounting bracket.
 2. The post assembly of claim 1, wherein the wall mount assembly is movably engaged with the upright to permit vertical movement of the upright when the wall mount assembly is fixedly mounted to the building structure.
 3. The post assembly of claim 1, wherein the hydraulic cylinder comprises a double-acting hydraulic cylinder.
 4. The post assembly of claim 3, wherein the wall mount assembly comprises a square tube that houses the elongated strut, the square tube having a plurality of bearings to permit the elongated strut to move vertically within the square tube.
 5. The post assembly of claim 1, wherein the elongated strut is housed within the slide tube and the cylinder mounting bracket, and the slide tube and cylinder mounting bracket comprise a plurality of bearings to permit the slide tube and cylinder mounting bracket to move vertically on the strut.
 6. The post assembly of claim 5, wherein the elongated strut, slide tube and cylinder mounting bracket comprise square tube.
 7. The post assembly of claim 1, wherein the elongated strut comprises a plurality of vertically spaced apertures, the first locking means comprises a first pin for engagement with the apertures and the second locking means comprises a second pin for engagement with the apertures.
 8. The post assembly of claim 7, wherein the first pin or the second pin or both the first pin and the second pin are biased for engagement within the apertures to prevent the slide tube and/or the cylinder mounting bracket from sliding down the strut.
 9. The post assembly of claim 8, wherein the first pin or the second pin or both the first pin and the second pin are biased by means of a spring.
 10. The post assembly of claim 9, wherein the first pin, the second pin or both the first pin and the second pin comprise means for selective disengagement from the apertures.
 11. The post assembly of claim 10, wherein the means for selective disengagement comprises a swivel link.
 12. The post assembly of claim 1, wherein the two or more platform support arms comprise an upper platform support arm for supporting a loader platform and a lower platform support arm for supporting a walker platform, the upper and lower platform support arms mounted to the slide tube on opposite sides of the elongated strut.
 13. The post assembly of claim 1, further comprising a foot connected to the upright proximal the bottom end of the elongated strut, the foot comprising a flat plate perpendicular to the elongated strut.
 14. The post assembly of claim 1, wherein at least one of the platform support arms is positioned between the first and second ends of the hydraulic cylinder.
 15. A height adjustable scaffolding system comprising: (a) two or more post assemblies as defined in claim 1, the upright of each post assembly spaced-apart from and mounted to the building structure; (b) two or more platforms extending between adjacent post assemblies supported on the platform support arms of the adjacent post assemblies; (c) a power source for powering the hydraulic cylinder of each post assembly; and, (d) control means for providing simultaneous control of power to all of the hydraulic cylinders.
 16. The system of claim 15, wherein the hydraulic cylinders are double-acting hydraulic cylinders.
 17. The system of claim 15, further comprising means for providing simultaneous selective disengagement of the first locking means from the elongated strut and means for providing simultaneous selective disengagement of the second locking means from the elongated strut.
 18. The system of claim 17, wherein the elongated strut comprises a plurality of vertically spaced apertures, the first locking means comprises a first pin for engagement with the apertures and the second locking means comprises a second pin for engagement with the apertures.
 19. The system of claim 15, wherein the one or more platform support arms comprise an upper platform support arm for supporting a loader platform and a lower platform support arm for supporting a walker platform, the upper and lower platform support arms mounted to the slide tube on opposite sides of the elongated struts, the walker platform and loader platform being on opposite sides of the elongated struts.
 20. The system of claim 15, wherein the wall mount assembly of each post assembly is movably engaged with its corresponding upright to permit vertical movement of the uprights relative to the wall mount assemblies. 